component testing with keysight dsox1102g scope

While reworking, you may want to redo C14 as per instructions.

John, advise for when you’re building the next kit, and you’re still learning electronics:

Try to stay closer to the instructions. The buildup is expected to be done in stages, then tested before you continue.

The issue at hand would then have been detected at page 10 during the power up test. At that time, there were 50% less components on the PCB that coul be the culprit. That could have helped narrowing the issue.

The intermediate tests they propose are also nicely isolated training opportunities because the scope is limited at each phase of the buildup + test cycle.

thanks jan

advice accepted .

john

Let us know how the fix worked. I'm hoping the radio will work now.

yes you are right.the small tab on pot base needs to fit in the closest slot, although i am not sure it is soldered in.it is underneath the base when pot is on the board, making it difficult to solder.

thnaks

john

just curious, why do you think they recommend this capacitor placed on the copper side?not talked about in instructions.

john

Hi John,

I think it's just in case it gets fitted back-to-front by mistake, or gets dented or some other damage. Because it's a large capacitor connected to the supply rails, they may have worried it could burst.. i.e. not pleasant on the side of the board facing the user. They can vent vertically, either from the metal circle portion, or the underside black portion.

he's the pot shell bas e does have a small tab on bottoms guess that should fit it the closest slot.but not sure it should be soldered?as it is underneath the base, hard to get to.the instructions not to solder 5 lugs' guess 3 wipers and 2 switch lugs, no mention of the small tab.

thanks

john

Hi John,

It (mostly) doesn't matter electrically. As you say, it's just a 3 terminal potentiometer, and a switch. You can use judgement to determine if that lug needs soldering or not (e.g. based on how physically strong it is, etc.

the small tab should not be soldered.

edit: some background on that:

All the contacts are made of a compliant metal. When force is put on the potentiometer, the flex in the leads will absorb it and little force goes to the solder pad.

The tab is made of hard iron and its role is to physically prevent rotation/slip. It's non-compliant, and any force on it is directly transferred to the sides of the hole it's mounted in.

If you solder this, slip force will be put on the (weak by nature) solder joint. It either will crack or tear the pad off the PCB.